天然气-柴油 双燃料发动机实现高压缩比的柔性活塞设计外文翻译资料

Reconfigurability of engines: A kinematic approach to variable compression ratio engines

Thiago Hoeltgebaum , Roberto Simoni, Daniel MartinsFederal University of Santa Catarina, Santa Catarina, Brazil

abstract

The variable compression ratio (VCR) engine has become an opportunity to overcome the new consumption and emissions laws. Researchers believe that the VCR engine can unite both efficiency and performance. Thus, it is applied a methodology based on Tsai (2000) and Yan(1998) in order to investigate the opportunities for the development of VCR engines. A patent survey was conducted analyzing 1163 patents and resulting in 127 different VCR engine designs. Based on that survey and comparing with several authors, this paper proposes an enhanced classification of the VCR engines. The kinematic chains from all classes of VCR engines are analyzed in order to investigate the topological and structural characteristics which are compared with previous works from Freudenstein and Maki (1983) and Tsai (2000). This information is used to discuss both the reconfigurability and the potential for innovation of VCR engines.

1. Introduction

Nicolaus Otto arguably created the internal combustion engine for commercial purposes in 1876 [4]. Since then, this field experienced several improvements and inventions. For instance, different operation cycles were created, several fuels became avail-able and the electronics played an important role in the optimization of the engine operation points. In addition, mechanism and machine design methodologies flourished in the last century making the design process more systematic and with a better view of the problem. An interesting review on design methodologies can be addressed at Dimarogonas [5].Even with several improvements in engine design, the new methodologies can provide different opportunities for innovation.Nowadays, one of the challenges for the automotive industry is to meet the emissions and fuel consumption standards. In Europe,the passenger vehicles will have to meet a 25 km/l average up to 20201. In USA, the passenger vehicles must be able to perform a23 km/l average up to 20252. In Brazil, the government will provide tax discounts for manufacturers able to meet the new standards for 2017, which are 17.26 km/l average for petrol and 11.76 km/l for ethanol.3Several authors believe the variable compression ratio engine (VCR) could be the technology to meet those standards. Erikssonand Neilsen [6] believe that the VCR engines could take two steps towards improved engine performance:

bull;The removal of the design trade-off between efficiency and engine knock;

bull; The possibility of downsizing and supercharging for improved fuel economy.

Gupta [7] states that modern engines have to satisfy the customer requirements for a high power output as well as for low fuel consumption and both objectives can be accomplished by a VCR engine. Rajput [8] observes that a fixed compression ratio engine cannot meet the various requirements of high specific output. Hence, the development of variable compression ratio enginesseems to be a necessity.According to Nilsson [9], the efficiency (eta;) of an engine can be estimated by

where rc is the compression ratio and gamma; is a thermodynamic constant. Eq. (1) shows that the higher the compression ratio, the higher the efficiency. However, in a real engine cycle, some energy is lost due to heat transfer and, therefore, the maximum efficiency is found at a limited compression ratio, normally below 16:1 [9].

Nilsson [9] states that a high compression ratio would be employed at low loads to maximize the efficiency. On the other hand, the low compression ratio would be used at high-loads to avoid knock. According to him, the benefits of variable compression ratio are more significant combined with downsizing and supercharging. Thus, it is possible to have either an efficient and powerful engine at the same time.

The first aim of this paper is to present an enhanced classification of VCR engines. To do so, this paper will present the representative designs for each class extracted from a patent survey and analyze their kinematic chains emphasizing mobility,number of loops, actuation, fractionation and order of screw system.

The second aim of this paper is to analyze the functional and structural requirements from the VCR engines kinematic chains.Freudenstein and Maki [3] have an important contribution on the development of reconfigurable engines. Nevertheless, theyshow a procedure for the synthesis of Variable Stroke engines. In Freudenstein and Maki [3] it is possible to find the functionaland structural requirements as well as the criteria to select kinematic chains for Variable Stroke engines. Tsai [1] has also contrib-uted for the development of variable stroke engines presenting several functional and structural requirements for the synthesis of such engines. Thus, the functional and structural requirements as well as the selection criteria presented by both authors will be taken into account when analyzing the characteristics of VCR engines.

The third aim of this paper is to discuss the reconfigurability of VCR engines from the point of view of mechanism theory,which is done (up to the authors knowledge) for the first time in the literature. To do so, the degrees of freedom of each VCR engine class will be investigated and the reconfigurability will be identified. The VCR engines usually have two degrees of freedom(2-DOF):

bull; The core DOF: The crankshaft rotary motion which is always actuated whenever the engine is operating;

bull; The reconfigurability DOF, which is the compression ratio control.

The reconfigurability DOF can be continuously actuated, be previously set or be discretely actuated to reconfigure the engine,i.e., a VCR engine can change its configuration during operation to meet the emissions and

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Reconfigurability of engines: A kinematic approach to variable compression ratio engines

Thiago Hoeltgebaum , Roberto Simoni, Daniel MartinsFederal University of Santa Catarina, Santa Catarina, Brazil

abstract

The variable compression ratio (VCR) engine has become an opportunity to overcome the new consumption and emissions laws. Researchers believe that the VCR engine can unite both efficiency and performance. Thus, it is applied a methodology based on Tsai (2000) and Yan(1998) in order to investigate the opportunities for the development of VCR engines. A patent survey was conducted analyzing 1163 patents and resulting in 127 different VCR engine designs. Based on that survey and comparing with several authors, this paper proposes an enhanced classification of the VCR engines. The kinematic chains from all classes of VCR engines are analyzed in order to investigate the topological and structural characteristics which are compared with previous works from Freudenstein and Maki (1983) and Tsai (2000). This information is used to discuss both the reconfigurability and the potential for innovation of VCR engines.

1. Introduction

Nicolaus Otto arguably created the internal combustion engine for commercial purposes in 1876 [4]. Since then, this field experienced several improvements and inventions. For instance, different operation cycles were created, several fuels became avail-able and the electronics played an important role in the optimization of the engine operation points. In addition, mechanism and machine design methodologies flourished in the last century making the design process more systematic and with a better view of the problem. An interesting review on design methodologies can be addressed at Dimarogonas [5].Even with several improvements in engine design, the new methodologies can provide different opportunities for innovation.Nowadays, one of the challenges for the automotive industry is to meet the emissions and fuel consumption standards. In Europe,the passenger vehicles will have to meet a 25 km/l average up to 20201. In USA, the passenger vehicles must be able to perform a23 km/l average up to 20252. In Brazil, the government will provide tax discounts for manufacturers able to meet the new standards for 2017, which are 17.26 km/l average for petrol and 11.76 km/l for ethanol.3Several authors believe the variable compression ratio engine (VCR) could be the technology to meet those standards. Erikssonand Neilsen [6] believe that the VCR engines could take two steps towards improved engine performance:

bull;The removal of the design trade-off between efficiency and engine knock;

bull; The possibility of downsizing and supercharging for improved fuel economy.

Gupta [7] states that modern engines have to satisfy the customer requirements for a high power output as well as for low fuel consumption and both objectives can be accomplished by a VCR engine. Rajput [8] observes that a fixed compression ratio engine cannot meet the various requirements of high specific output. Hence, the development of variable compression ratio enginesseems to be a necessity.According to Nilsson [9], the efficiency (eta;) of an engine can be estimated by

where rc is the compression ratio and gamma; is a thermodynamic constant. Eq. (1) shows that the higher the compression ratio, the higher the efficiency. However, in a real engine cycle, some energy is lost due to heat transfer and, therefore, the maximum efficiency is found at a limited compression ratio, normally below 16:1 [9].

Nilsson [9] states that a high compression ratio would be employed at low loads to maximize the efficiency. On the other hand, the low compression ratio would be used at high-loads to avoid knock. According to him, the benefits of variable compression ratio are more significant combined with downsizing and supercharging. Thus, it is possible to have either an efficient and powerful engine at the same time.

The first aim of this paper is to present an enhanced classification of VCR engines. To do so, this paper will present the representative designs for each class extracted from a patent survey and analyze their kinematic chains emphasizing mobility,number of loops, actuation, fractionation and order of screw system.

The second aim of this paper is to analyze the functional and structural requirements from the VCR engines kinematic chains.Freudenstein and Maki [3] have an important contribution on the development of reconfigurable engines. Nevertheless, theyshow a procedure for the synthesis of Variable Stroke engines. In Freudenstein and Maki [3] it is possible to find the functionaland structural requirements as well as the criteria to select kinematic chains for Variable Stroke engines. Tsai [1] has also contrib-uted for the development of variable stroke engines presenting several functional and structural requirements for the synthesis of such engines. Thus, the functional and structural requirements as well as the selection criteria presented by both authors will be taken into account when analyzing the characteristics of VCR engines.

The third aim of this paper is to discuss the reconfigurability of VCR engines from the point of view of mechanism theory,which is done (up to the authors knowledge) for the first time in the literature. To do so, the degrees of freedom of each VCR engine class will be investigated and the reconfigurability will be identified. The VCR engines usually have two degrees of freedom(2-DOF):

bull; The core DOF: The crankshaft rotary motion which is always actuated whenever the engine is operating;

bull; The reconfigurability DOF, which is the compression ratio control.

The reconfigurability DOF can be continuously actuated, be previously set or be discretely actuated to reconfigure the engine,i.e., a VCR engine can change its configuration during operation to meet the emissions and

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