Optimization of Waste Gate Drive Circuit of Two-Stage Turbocharging System

A two stage turbocharging control system was proposed,in which the pressure regulator valve with a close-loop pressure adjusting function instead of a high speed on-off solenoid valve,is used as a driving mechanism of waste gate.A digital-analog（DA）conversion circuit based on pulse width modulation（PWM）generates one analog voltage signal required by the pressure regulating valve control.The principle of the DA conversion circuit was analyzed,meanwhile,the performance of the conversion circuit was improved by adopting a speed-up capacitor,which helps to increase the stability and responsiveness of the control voltage generated by the conversion circuit;the structure parameters of the circuit was optimized by simulation.After the optimization,the ripple wave of circuit output voltage was kept within16mV under the 12bit conversion accuracy,the conversion time of the circuit could be reduced to 4ms.The engine bench test show that the turbocharging boost pressure control system which adopted the circuit had a rather good stable control accuracy（the steady state within 0.8%）and dynamic response（the regulation time is less than 4s）.

Turbocharging the DA465 gasoline engine

In order to improve performance of the DA465Q gasoline engine, a substantial amount of research was done to optimize its turbocharging system. The research led to the GT12 turbocharger being selected and its turbocharging parameters being settled. Based on these tests, rational matching was worked out for respective components of the turbocharging system. Results show that this turbocharger allows the engine to easily meet the proposed requirements for power and economic performance, giving insight into further performance improvements for gasoline engines.

Analysis of the Behavior of a Turbomachine Driven by a Compressed Air System

Different experiments in high speed turbomachines require expensive and sophisticated infrastructure to implement their impulsion and reach high regimes. In developed countries, this can be achieved by using aeroderivative gas turbines or DC motors of about 400 HP. This paper presents an experimental system designed and built with the intention of performing behavior studies in test turbomachinery. The proposed installation uses compressed air as driving fluid, which allows the turbomachinery to reach high rotational speeds where very important phenomena occur. An analysis is carried out considering the rotational speed behavior of an internal combustion engine turbocharger of the Perkins series when it is driven by pressures ranging from 4.2 kg/cm2 to zero. Additionally, another experiment couples an automotive electrical generator with the turbine to observe the system operation when a load is applied. The behavior of the pressure is analyzed when it is in function of the time of air discharge that goes from a compressed air storage tank to the turbocharger for its impulsion. This is an experimental system that can be designed and constructed economically within the bounds of any public university.

Thermodynamic Analysis of Turbo-Charged Power Generating System

Turbochargers have been known in compression ignition engines for power generation.Recent trends in power generation through gas cycles have recorded successes via turbochargers application in spark ignition engines as well.When power cycles are turbocharged,there is a general expectation of a higher power and performance output from the cycle as compared to when they are naturally aspirated.This research was conducted to estimate the thermodynamic properties of a spark ignition engine power generating system when it is both naturally aspirated and when the same system is turbocharged to 2.5 times the amount of air in natural aspiration.Octane fuel was employed for petrol approximation during this study.The system process was broken down into stages of charging between natural aspiration and turbocharged;thus MATLAB program was applied to model the system for the case of natural aspiration and turbocharging with no increase in fuel supply.The results were used for both analyses and comparison which showed that the system generates slightly more power with turbocharging at 0%increase in fuel consumption.The natural aspiration achieved values are 2.8232 kJ/mol and 55.26%for output and efficiency respectively,while the turbocharged engine produced optimal values of 2.8833 kJ/mol and 56.51%for output and efficiency.The air fuel ratio by mole for the turbocharged engine was 145.18:1,which shows a greater fuel economy of 59%as compared to the 59.5:1 A/F(air/fuel)ratio of the naturally aspirated engine.

双燃料船用发动机废能回收系统的技术经济比较

Nowadays alternative and innovative energy recovery solutions are adopted on board ships to reduce fuel consumption and harmful emissions.According to this,the present work compares the engine exhaust gas waste heat recovery and hybrid turbocharger technologies,which are used to improve the efficiency of a dual-fuel four-stroke(DF)marine engine.Both solutions aim to satisfy partly or entirely the ship’s electrical and/or thermal loads.For the engine exhaust gas waste heat recovery,two steam plant schemes are considered:the single steam pressure and the variable layout(single or dual steam pressure plant).In both cases,a heat recovery steam generator is used for the electric power energy generation through a steam turbine.The hybrid turbocharger is used to provide a part of the ship’s electric loads as well.The thermodynamic mathematical models of DF engines,integrated with the energy recovery systems,are developed in a Matlab-Simulink environment,allowing the comparison in terms of performance at different engine loads and fuels,which are Natural Gas(NG)and High Fuel Oil(HFO).The use of NG always involves better efficiency of the system for all the engine working conditions.It results that the highest efficiency value achievable is 56%at 50%maximum continuous rating(MCR)engine load.

A Strategy to Control the Turbocharger Energy of a Diesel Engine at Different Altitudes

Power deterioration is a major problem for diesel engines operating at high altitudes.This problem stems from the limited availability of turbocharger energy,which is not enough to increase the boost pressure to the required level.In this study,a control strategy is introduced in order to achieve engine power recovery at different altitudes.It is shown that as the altitude increases from 0 to 4500 m,the required boost pressure ratio increases from 2.4 to 4.3.The needed turbocharger energy should be increased accordingly by 240%,and the TCC(turbine characterization coefficient)should be adjusted within wide ranges.A 12%decrease in the TCC can lead to a rise of the intake air pressure,which can compensate the pressure decrease due to a 1000 m altitude increase.The fluctuation range of boost pressure was within 14.5 kPa for variations in altitude from 0 to 4500 m.

Development of Turbocharger for Improving Diesel Engine Matching Performance

The two development ways of turbocharger technology to solve the problem of matching performance with diesel were presented. The ways of waste valve gate turbocharger and variable geometry turbocharger can solve the problem of engine’s low speed torque and achieve lower smoke level. Especially for variable geometry turbocharger, it covers all conditions of engine. It can not only improve the low engine’s speed torque and keep the power performance at high engine speed, but also cover wide engine speed performance that keeps lower fuel consumption and exhaust gas temperature in full load and part load matching. The results of theory analysis and experiment research showed that it’s the ideal solution to solve the matching problem of diesel engines.

Effects of Floating Ring Bearing Manufacturing Tolerance Clearances on the Dynamic Characteristics for Turbocharger

The inner and outer oil film dynamic characteristic coefficients of floating ring bearings（FRBs） change due to the manufacturing tolerance of the floating ring, journal and intermediate, which leads to high-speed turbocharger＇s vibration too large and even causes nonlinear vibration accident. However, the investigation of floating ring bearing manufacturing tolerance clearance on the rotordynamic characteristics is less at present. In order to study the influence law of inner and outer clearance on turbocharger vibration, the rotor dynamic motion equations of turbocharger supported in FRBs are derived by analyzing the size relations between floating ring, journal and intermediate for the inner and outer oil film clearances, the time transient response analysis for combination of FRBs clearance are developed. A realistic turbocharger is taken as a research object, the FE model of the turbocharger with FRBs is modeled. Under the conditions of four kinds of limit state bearing clearances for inner and outer oil film, the nonlinear transient analyses are performed based on the established FE dynamic models of the nonlinear rotor-FRBs system applied incentive combinations of gravity and unbalance force, respectively. From the waterfall, the simulation results show that the speed for the appearance of fractional frequency is not identical and the amplitude magnitude is different under the four kinds of bearing manufacturing tolerance limit clearances, and fractional frequency does not appear in the turbocharger and the amplitude is minimum under the ODMin/IDMax bearing manufacturing tolerance clearances. The turbocharger vibration is reduced by controlling the manufacturing tolerance clearance combinations of FRBs, which is helpful for the dynamic design and production-manufacturing of high-speed turbocharger.

Time-dependent Vibration Frequency Reliability Analysis of Blade Vibration of Compressor Wheel of Turbocharger for Vehicle Application

Blade vibration failure is one of the main failure modes of compressor wheel of turbocharger for vehicle application. The existing models for evaluating the reliability of blade vibration of compressor wheel are static, and can not reflect the relationship between the reliability of compressor wheel with blade vibration failure mode and the life parameter. For the blade vibration failure mode of compressor wheel of turbocharger, the reliability evaluation method is studied. Taking a compressor wheel of turbocharger for vehicle application as an example, the blade vibration characteristics and how they change with the operating parameters of turbocharger are analyzed. The failure criterion for blade vibration mode of compressor wheel is built with the Campbell diagram, and taking the effect of the dispersity of blade natural vibration frequency and randomness of turbocharger operating speed into account, time-dependent reliability models of compressor wheel with blade vibration failure mode are derived, which embody the parameters of blade natural vibration frequency, turbocharger operating speed, the blade number of compressor wheel, life index and minimum number of resonance, etc. Finally, the rule governing the reliability and failure rate of compressor wheel and the method for determining the reliable life of compressor with blade vibration is presented. A method is proposed to evaluate the reliability of compressor wheel with blade vibration failure mode time-dependently.

Effects of Semi-floating Ring Bearing Outer Clearance on the Subsynchronous Oscillation of Turbocharger Rotor

Semi-floating ring bearing（SFRB） is developed to control the vibration of turbocharger rotor. The outer clearance of SFRB affects the magnitude and frequency of nonlinear whirl motion, which is significant for the design of turbocharger. In order to explore the effects of outer clearance, a transient finite element analysis program for rotor and oil film bearing is built and validated by a published experimental case. The nonlinear dynamic behaviors ofrotor-SFRB system are simulated. According to the simulation results, two representative subsynchronous oscillations excited by the two hearings respectively are discovered. As the outer clearance of SFRB increases from 24 ~tm to 60 pro, the low-frequency subsynchronous oscillation experiences three steps, including a strong start, a gradual recession and a combination with the other one. At the same time, the high-frequency subsynchronous oscillation starts to appear gradually, then strengthens, and finally combines. If gravity and unbalance are neglected, the combination will start starts from high rotor speed and extents to low rotor speed, just like a ＂zipper＂. It is found from the quantitative analysis that when the outer clearance increases, the vibration amplitude experiences large value firstly, then reduction, and suddenly increasing after combination. A useful design principle of SFRB outer clearance for minimum vibration amplitude is proposed： the outer clearance value should be chosen to keep the frequency of two subsynchronous oscillations clearly separated and their amplitudes close.

Semi-solid moulding:Competition to cast and machine from forging in making automotive complex components

The very latest technique for impeller manufacture is called semi-solid moulding(SSM).Cummins Turbo Technologies Limited,together with Aluminum Complex Components Inc,developed SSM compressor wheels as a way of achieving cost and durability performance somewhere between that of cast and machined from solid(MFS) aluminium alloy wheels.Experimental results show SSM material has a superior microstructure and mechanical properties over cast and comparable to MFS materials.Component testing including durability testing,using accelerated speed cycle tests,proves SSM compressor wheels emerge as being significantly more durable than cast equivalents and approaching that of MFS impellers.Further challenges for semi-solid processing in manufacture of other complex components and other materials in automotive industry in terms of both cost and durability are also discussed.

Elimination of misrun and gas hole defects of investment casting TiAl alloy turbocharger based on numerical simulation and experimental study

Casting technology of thin-wall TiAl alloy turbochargers was studied by investment casting and numerical simulation.Misruns and gas holes were the main defects observed in preliminary work due to the poor fluidity of alloy,and to gas entrapment.In order to eliminate these defects,cast parameters,such as centrifugal rotation rate and mould preheating temperature,were optimized by numerical simulation,meanwhile,the structure of the shell mould was optimized to improve the filling capacity of TiAl alloy.Pouring experiments were carried out by vacuum induction melting furnace equipped with a water-cooled copper crucible based on the above optimization.The quality of the TiAl alloy casting was analyzed by fluorescent penetrant inspection and X-ray detection.The results show that a centrifugal rotation rate of 200 rpm,mould preheating temperature of 600°C,shell preparation through organic fiber addition can dramatically improve the mould filling capacity,and integrated turbochargers were finally prepared.

Rotor dynamic analysis of small vehicle gasoline turbocharger in semi-floating bearings

The critical speed and unbalance response of a small vehicle gasoline turbocharger in semi-floating bearing are analyzed.The dynamical characters of semi-floating bush bearing used in small vehicle gasoline turbocharger were summarized by comparing the structure and shaft rigid mode of semi-floating bush bearings with those of floating bush bearings.The rotor model was built.The first,second and third mode of critical speeds of rotor system were computed,and the changes in the compressor or turbine bushing bearing clearances were analyzed.Compared with the experiment data,the accuracy and the rationality of computation model were verified.The unbalance response and time transient rotor response were also computed.

High-quality aluminum turbocharger impellers produced by thixocasting

The thixocasting process was chosen to produce the impellers as it is capable of producing castings with extremely high internal quality.Slugs cut from the DC cast bars are re-heated to the semi-solid casting temperature, and a specially-designed runner and gating system is used to prevent oxide from the surface of the slugs from becoming incorporated into the impeller.The technology used to produce the semi-solid impellers is described in detail.The semi-solid cast impellers, produced from an Al-Si-Mg-Cu alloy, are heat treated to the T6 temper.Results from testing are presented demonstrating that the impellers are free of porosity and other internal defects.Both mechanical property and fatigue data are presented showing that the semi-solid impellers have better properties than impellers produced by conventional casting and similar properties to forged and machined impellers.A short study is also described which identified suitable processing parameters to minimize hot tearing in the complex-shaped turbocharger impellers semi-solid cast from alloy 201.The surfaces of the impellers were examined using penetrant testing, and the results of modifying processing parameters on the propensity for surface cracking are presented.An aging study was performed to identify optimum mechanical strength.

Research on the Critical Speed of a Mixed-Flow Turbocharger with Hybrid Ceramic Ball Bearing

The critical speeds for a vehicle turbocharger with hybrid ceramic ball bearing are researched. The ball bearing-rotor system produces resonance when it working in critical speed and that makes the turbocharger injury working for a long time. The calculation and analysis methods of the critical speed for the vehicle turbocharger are described. The critical speed is computed by two methods including Riccati transfer matrix and DyRoBeS finite element method for a vehicle turbocharger with hybrid ceramic ball bearing. The vibration experiment had been taken to validate the calculating result, Comparison between the results by two calculation methods and the test results show that the first critical speed differences are 6.47 % and 5.66 %, the second critical speed differences are 2.87 % and 2.94 % respectively. And then, the primary factors which influence the critical speed are analyzed, the conclusions will be helpful for the vehicle turbocharger bearing-rotor system design.

Method for Evaluating the Reliability of Compressor Impeller of Turbocharger for Vehicle Application in Plateau Area

As turbocharging diesel engines for vehicle application are applied in plateau area, the environmental adaptability of engines has drawn more attention. For the environmental adaptability problem of turbocharging diesel engines for vehicle application, the present studies almost focus on the optimization of performance match between turbocharger and engine, and the reliability problem of turbocharger is almost ignored. The reliability problem of compressor impeller of turhocharger for vehicle application when diesel engines operate in plateau area is studied. Firstly, the rule that the rotational speed of turbocharger changes with the altitude height is presented, and the potential failure modes of compressor impeller are analyzed. Then, the failure behavior models of compressor impeller are built, and the reliability models of compressor impeller operating in plateau area are developed. Finally, the rule that the reliability of compressor impeller changes with the altitude height is studied, the measurements for improving the reliability of the compressor impellers of turbocharger operating in plateau area are given. The results indicate that when the operating speed of diesel engine is certain, the rotational speed of turbocharger increases with the increase of altitude height, and the failure risk of compressor impeller with the failure modes of hub fatigue and blade resonance increases. The reliability of compressor impeller decreases with the increase of altitude height, and it also decreases as the increase of number of the mission profile cycle of engine. The method proposed can not only be used to evaluating the reliability of compressor impeller when diesel engines operate in plateau area but also be applied to direct the structural optimization of compressor impeller.

Effects of Unbalance Location on Dynamic Characteristics of High-speed Gasoline Engine Turbocharger with Floating Ring Bearings

For the high-speed gasoline engine turbocharger rotor, due to the heterogeneity of multiple parts material, manufacturing and assembly errors, running wear in impeller and uneven carbon of turbine, the random unbalance usually can be developed which will induce excessive rotor vibration, and even lead to nonlinear vibration accidents. However, the investigation of unbalance location on the nonlinear high-speed turbocharger rotordynamic characteristics is less. In order to discuss the rotor unbalance location effects of turbocharger with nonlinear floating ring bearings（FRBs）, the realistic turbocharger of gasoline engine is taken as a research object. The rotordynamic equations of motion under the condition of unbalance are derived by applied unbalance force and nonlinear oil film force of FRBs. The FE model of turbocharger rotor-bearing system is modeled which includes the unbalance excitation and nonlinear FRBs. Under the conditions of four different applied locations of unbalance, the nonlinear transient analyses are performed based on the rotor FEM. The differences of dynamic behavior are obvious to the turbocharger rotor systems for four conditions, and the bifurcation phenomena are different. From the results of waterfall and transient response analysis, the speed for the appearance of fractional frequency is not identical and the amplitude magnitude is different from the different unbalance locations, and the non-synchronous vibration does not occur in the turbocharger and the amplitude is relative stable and minimum under the condition 4. The turbocharger vibration and non-synchronous components could be reduced or suppressed by controlling the applied location of unbalance, which is helpful for the dynamic design, fault diagnosis and vibration control of the high-speed gasoline engine turbochargers.

Research on the Control Strategy of Variable Nozzle Turbocharger for Natural Gas Engine

A variable nozzle turbocharger （VNT） was applied to a 2.2-liter L4 natural gas engine,and a VNT control system was designed to operate it.Based on VNT matching test results,a VNT control strategy was studied,in which VNT adjustment is carried out through pre-calibrated VNT handling rod position,combined with a closed-loop target boost pressure feedback using proportional-integral-derivative（PID） algorithm.Experimental results showed that the VNT control system presented in this thesis can lead to optimized performance of VNT,increase engine volumetric efficiency over a wide speed range,improve engine dynamic characteristics and upgrade economic performance.

Computation of the Matching Performance of Diesel Engine with Variable Geometry Turbocharger

To compute the matching performance of diesel engine with variable geometry turboeharger（VGT）, the formerly used program is improved through adjustment of turbine mass flow rate and efficiency characteristics. The calculation result is applied to forecast the performance of J6110Z diesel engine with rotary-vaned VGT70, and to guide the improvement of engine fuel supply. The computed engine performance curve coincides with the experiment result well： the low-speed torque, fuel economy, exhaust temperature and boost pressure of the VGT engine are all improved.

Collaborative optimization of exhaust gas recirculation and Miller cycle of two-stage turbocharged marine diesel engines based on particle swarm optimization

To meet increasingly stringent emission standards and lower the brake-specific fuel consumption(BSFC)of marine engines,a collaborative optimization study of exhaust gas recirculation(EGR)and a Miller cycle coupled turbocharging system was carried out.In this study,a one-dimensional numerical model of the EGR,Miller cycle,and adjustable two-stage turbocharged engine based on WeiChai 6170 marine diesel engine was established.The particle swarm optimization algorithm was used to achieve multi-input and multi-objective comprehensive optimization,and the effects of EGR-coupled Miller regulation and high-pressure turbine bypass regulation on NO_(x)and BSFC were investigated.The results showed that a medium EGR rate-coupled medium Miller degree was better for the comprehensive optimization of NO_(x)and BSFC.At medium EGR rate and low turbine bypass rates,NO_(x)and BSFC were relatively balanced and acceptable.Finally,an optimal steady-state control strategy under full loads was proposed.With an increase in loads,the optimized turbine bypass rate and Miller degree gradually increased.Compared with the EGRonly system,the optimal system of EGR and Miller cycle coupled turbine bypass reduced NO_(x)by 0.87 g/(kW·h)and BSFC by 17.19 g/(kW·h)at 100%load.Therefore,the EGR and Miller cycle coupled adjustable two-stage turbocharging achieves NO_(x)and BSFC optimization under full loads.