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Technical Paper

Study on Fuel Economy Improvement by Low Pressure Water-Cooled EGR System on a Downsized Boosted Gasoline Engine

This research was concerned with the use of Exhaust Gas Recirculation (EGR) improving the fuel economy over a wide operating range in a downsized boosted gasoline engine. The experiments were performed in a 1.3-Litre turbocharged PFI gasoline engine, equipped with a Low Pressure (LP) water-cooled EGR system. The operating conditions varied from 1500rpm to 4000rpm and BMEP from 2bar to 17bar. Meanwhile, the engine’s typical operating points in NEDC cycle were tested separately. The compression ratio was also changed from 9.5 to 10.5 to pursue a higher thermal efficiency. A pre-compressor throttle was used in the experiment working together with the EGR loop to keep enough EGR rate over a large area of the engine speed and load map. The results indicated that, combined with a higher compression ratio, the LP-EGR could help to reduce the BSFC by 9∼12% at high-load region and 3∼5% at low-load region.
Technical Paper

Optimization of Control Strategy for Engine Start-stop in a Plug-in Series Hybrid Electric Vehicle

Plug-in hybrid electric vehicles (PHEVs) provide significantly improvement in fuel economy over conventional vehicles as well as reductions in greenhouse gas and petroleum. Numerous recent reports regarding control strategy, power train configuration, driving pattern, all electric range (AER) and their effects on fuel consumption and electric energy consumption of PHEVs are reported. Meanwhile, the control strategy for engine start-stop and mileage between recharging events from the electricity grid also has an important influence on the petroleum displacement potential of PHEVs, but few reports are published. In this paper, a detailed simulation model is set up for a plug-in series hybrid electric vehicle (PSHEV) employing the AVL CRUISE. The model was employed to predict the AER of the baseline PSHEV using rule-based logical threshold switching control strategy.
Technical Paper

Improvement on Energy Efficiency of the Spark Ignition System

Future clean combustion engines tend to increase the cylinder charge to achieve better fuel economy and lower exhaust emissions. The increase of the cylinder charge is often associated with either excessive air admission or exhaust gas recirculation, which leads to unfavorable ignition conditions at the ignition point. Advanced ignition methods and systems have progressed rapidly in recent years in order to suffice the current and future engine development, and a simple increase of energy of the inductive ignition system does not often provide the desired results from a cost-benefit point of view. Proper design of the ignition system circuit is required to achieve certain spark performances.
Technical Paper

Fuel Injection Optimization during Engine Quick Start by Means of Cycle-by-Cycle Control Strategy for HEV Application

Engine-off strategy are popular used in hybrid electric vehicles (HEV) for fuel saving. The engine of an HEV will start and stop frequently according to the road condition. In order to obtain excellent fuel economy and emissions performance, the fuel injection during engine quick start should be optimized. In this paper, the characteristic of mixture formation and the HC emissions at the first 5 cycles which contribute the most HCs were investigated. After the analysis of mixture preparation during start process, the HC emissions during engine quick start were optimized by means of cycle-by-cycle fuel injection control strategy. The fuel mixture concentration during start-up process fluctuates more dramatically under hot start condition. Typically, the mixture at 4th and 5th cycle is over-riched. Based on the original engine calibration, the fuel injection at the initial 5 cycles was optimized respectively.
Technical Paper

Effect of Two-Stage Valve Lift for Fuel Economy and Performance on a PFI Gasoline Engine

Reducing the pumping loss, and thus, the fuel consumption of gasoline engine at part load, a two-stage intake valve lift system was implanted into a PFI engine. A corresponding engine model was set up with GT-power as well, which can simulate the effect of two-stage intake valve lift and different EGR rates on fuel economy performance and on combustion condition of a gasoline engine. Based on simulation results, the valve lift control strategy and EGR control strategy was studied in this paper. Results showed that at low engine speed, when SMALL LIFT was used, the tumble flow and the combustion process in cylinder was improved and burn time duration became shorter, resulting in higher indicated efficiency and lower fuel consumption than by LARGE LIFT. With the introduction of the exhaust gas recirculation (EGR), lower fuel consumption was acquired.
Technical Paper

Effect of EGR Temperature on PFI Gasoline Engine Combustion and Emissions

In order to investigate the impacts of recirculated exhaust gas temperature on gasoline engine combustion and emissions, an experimental study has been conducted on a turbocharged PFI gasoline engine. The engine was equipped with a high pressure cooled EGR system, in which different EGR temperatures were realized by using different EGR coolants. The engine ran at 2000 r/min and 3000 r/min, and the BMEP varied from 0.2MPa to 1.0MPa with the step of 0.2MPa. At each case, there were three conditions: 0% EGR, 10% LT-EGR, 10% HT-EGR. The results indicated that LT-EGR had a longer combustion duration compared with HT-EGR. When BMEP was 1.0 MPa, CA50 of HT-EGR advanced about 5oCA. However, CA50 of LT-EGR could still keep steady and in appropriate range, which guaranteed good combustion efficiency. Besides, LT-EGR had lower exhaust gas temperature, which could help to suppress knock. And its lower exhaust gas temperature could reduce heat loss. These contributed to fuel consumption reduction.
Technical Paper

Design and Simulation of Serial Hybrid Electric Moped Powertrain

According to the requirements of two-wheel vehicle's future market and the characteristic of urban road conditions in China, the advantages and disadvantages of three basic configurations for the Hybrid Electric Vehicle are compared, finally, the serial hybrid configuration is chosen to be applied to hybrid Electric Moped solution. The selection principle of main components of this hybrid powertrain system includes ICE, generator, battery and hub motor, and the optimal match for performance parameters of these components are introduced in this paper. Then, a hybrid system model is established based on AVL-CRUISE. The simulations of fuel efficiency and exhaust emissions for both serial hybrid moped and conventional motorcycle is offered.
Technical Paper

Comparison of Fuel Economy Improvement by High and Low Pressure EGR System on a Downsized Boosted Gasoline Engine

In this paper comparisons were made between the fuel economy improvement between a High Pressure loop (HP) water-cooled Exhaust Gas Recirculation (EGR) system and a Low Pressure loop (LP) water-cooled EGR system. Experiments were implemented on a 1.3-Litre turbocharged PFI gasoline engine in two pars. One was EGR rate as single operating point to compare the different effect of HP- and LP-EGR. The other was mini map from 1500rpm to 3000rpm and BMEP from 2bar to 14bar because of the relative narrow available range of HP-EGR system. In consideration of practical application of EGR system, the coolant used in this experiment was kept almost the same temperature as in real vehicles (88±3°C) instead of underground water temperature, besides a model was built to calculate constant volume ratio (CVR). The results indicated that the effect of HP-EGR was weaker than that of LP-EGR under the same EGR rate, which could be seen from change of combustion parameters.
Technical Paper

Combined Technologies for Efficiency Improvement on a 1.0 L Turbocharged GDI Engine

The CO2 reduction request for automotive industry promotes the efforts on the engine thermal efficiency improvement. The goal of this research is to improve the thermal efficiency on an extremely downsized 3-cylinder 1.0 L turbocharged gasoline direct injection engine. Effects of compression ratio, exhaust gas recirculation (EGR), valve timing and viscosity of oil on fuel economy were studied. The results show that increasing compression ratio, from 9.6 to 12, can improve fuel economy at relative low load (below 12 bar BMEP), but has a negative effect at high load due to increased knock intensity. EGR can significantly reduce the pumping loss at low load, optimize combustion phase and reduce exhaust gas temperature. Therefore, the fuel consumption is reduced at all test points. The average brake thermal efficiency (BTE) benefit percentage is 3.47% with 9.6 compression ratio and 5.33 % with 12 compression ratio.
Technical Paper

Closed Loop Control of SI/HCCI Combustion Mode Switch Based on Ion Current Feedback

Gasoline direct injection (GDI) technology is admitted to be one of the most effective measures to improve the fuel economy for the spark ignition (SI) engines. Homogeneous Charge Compression Ignition (HCCI) combustion has advantages of low fuel consumption and ultra low NOx emissions. But the difficulty in the autoignition control and the narrow operation region inhibit the practical application of this technology. A hybrid combustion mode which combines SI mode and HCCI mode in separated working regions was regarded as a promising technology for HCCI engines. In addition, monitoring and providing feedback to the in-cylinder combustion characteristics is generally considered to be an effective method to improve and to optimize the combustion process. A lot of combustion information is included in the ion current generated by the in-cylinder combustion, and hence the ion current detection technique is considered to be a potential combustion feedback method.
Technical Paper

Auto-ignition Characteristics of Lubricant Droplets under Hot Co-Flow Atmosphere

It has been revealed by researches that lubricant properties have a great effect on the low-speed pre-ignition (LSPI) frequency in downsizing turbocharged direct-injection engines which are developed for better fuel economy. Droplets of lubricant or lubricant-gasoline mixture are considered to be the potential pre-ignition sources. Those droplets fly into the combustion chamber and ignite the gasoline-air mixture. To study lubricant droplets fundamentally, a novel set of droplet auto-ignition system is designed based on a Dibble Burner for this experiment. Influences of metallic additive contents, viscosities, lubricant diluted with gasoline and waste lubricant on the ignition delay of droplets are investigated by testing 12 groups of lubricants or lubricant-gasoline mixture. The equivalent diameter of each droplet generated by micro-syringes is around 2.1 mm. The co-flow temperature varies from 1123 K to 1223 K, and the experiments are carried out at atmospheric pressure.
Technical Paper

A Study on Combustion and Emission Characteristics of GDI Engine for HEV at Quick Start

Gasoline Direct Injection (GDI) engines have attracted interest as automotive power-plants because of their potential advantages in down-sizing, fuel efficiency and in emissions reduction. However, GDI engines suffer from elevated unburned hydrocarbon (HC) emissions during start up process, which are sometimes worsened by misfires and partial burns. Moreover, as the engine is cranked to idle speed quickly in HEVs (Hybrid Electric Vehicle), the transients of quick starts are more dramatically than that in traditional vehicle, which challenge the optimization of combustion and emissions. In this study, test bench had been set up to investigate the GDI engine performances for ISG (Integrated Starter and Generator) HEVs during start up process. Based on the test system, cycle-controlled of the fuel injection mass, fuel injection timing and ignition timing can be obtained, as well as the cycle-resolved measurement of the HC concentrations and NO emissions.