Equipment & Technology, Gas & Oil Fired, Strategic Development

A new engine design philosophy

Issue 5 and Volume 17.

Hyundai Heavy Industries (HHI) is continuously improving its methods for reciprocating engine development and its engine control systems. Computer-based technologies, which enable the optimization of engine performance and maintainability, are increasingly helpful in these processes, write Ki Hoon Jang and Seunghyup Ryu

Since the first announcement of the HiMSEN H21/32 in 2001, Hyundai Heavy Industries has been continuously developing not only diesel engines such as H25/33, H17/28, H32/40, H32/40V and H46 but also gas and dual fuel engines such as H35/40G, H35/40GV, H35DF and H27DF as part of the HiMSEN family. This range has been developed via the so-called Hi-Touch and Hi-Tech methodologies. This led to a successful place in the medium speed engine market in the past decade. The engines are used for stationary applications as well as marine applications. Thanks to support and co-operation from many customers, over 10,000 sets have been delivered.

A new design philosophy

In response to increasingly demanding customer needs and changes in the market, HiMSEN engine is pursuing a new design philosophy. The customers want to have low capex and low opex during the operational life of the engine.

The acronym CLEAN is used to illustrate the concept. Each letter in CLEAN has a meaning: C= Customer, L= reLiability, E = Environment, A = Acceptable technology and N = No defect. The new HiMSEN H21C diesel engine has been developed based on this new design philosophy. This engine has a bore of 210 mm and a stroke of 330 mm. The nominal running speed is 900 or 1000 rpm. By choosing the number of cylinders between five and nine, the output of this engine type ranges from 1.2 MW to 2.2 MW.

The reliable and robust design of engine structure helps to optimize the engine performance and efficiency under much higher-pressure combustion conditions than the former H21/32 HiMSEN engine. The HiMSEN H21C is equipped with a high-pressure mechanical fuel-injection system for low fuel consumption and stable engine operation. The dual valve timing (DVT) technology and the swirl of the combustion chamber help to improve the combustion performance and reduce the smoke, especially under low load operating conditions. The high efficiency turbocharging system and advanced Miller cycle technology are also adapted to fulfil increasingly stringent environmental regulations and fuel efficiency needs.

The New HiMSEN Design Philosophy

Engine design features

The HiMSEN H21C engine has been designed with a simple and modularized design concept. The modularization of engine components such as the fuel oil supply system contributes to improving maintainability by reducing the number of engine components. In addition, a low centre of gravity ensures structural stability of the engine for various operating conditions.

Comparing to the conventional HiMSEN engine, one of the biggest differences is the position of the charge air cooler. This cooler is mounted on the exhaust side of the engine so that the intake air enters into the middle of the air chamber. This helps to equalize the air flow to the engine cylinders and to minimize the differences in temperature of the intake air. In order to maximize the efficiency of the turbocharging process, the exhaust pipe has been straightened.

HiMSEN H21C engine

For facilitating maintenance, component dismantling has been minimized. It is possible to lift the cylinder head without dismantling any other engine components such as exhaust pipes and insulation covers. Pipe interconnections have been minimized for preventing oil leaks and damage caused by vibration and pulsation.

Furthermore, the fuel oil is supplied underneath the fuel oil injection pumps. It is therefore possible to remove the fuel oil injection pump unit without dismantling other components such as fuel feed pipes. The fuel oil feed system is structurally protected and covered so that contamination and other problems due to oil scattering can be prevented. Engine gallery, covers and display panels are optimized for the comfort of the user. All of these design improvements were carried out at the initial stage of engine development.

The main structures have been designed with computer aided engineering technologies and were subsequently fully verified by various analyses and internal tests. The engine block is made of grey cast iron and designed for a low stress level and light weight in spite of the increased power density. The passage of cooling water and lubrication oil is integrated into the engine block in order to minimize the external piping work and simplify the engine appearance.

The crankshaft is made of high tensile material such as Ni-Cr-Mo alloy steel in order to secure engine reliability. The elements of the crankshaft such as pin, journal and fillet have been designed by torsional vibration calculation and structural analysis.

The cylinder head is made of nodular cast iron. The fire deck of the cylinder head has been reinforced structurally in order to maintain durability with increasing engine power density. The HiMSEN Dual Valve Timing (DVT) system is also positioned inside of the cylinder head. This helps to improve the maintainability of DVT and simplifies the control system. In addition, in order to improve the fuel-air mixing rate in the combustion chamber, the swirl generation in the intake port has been increased.

The cylinder liner is made of grey cast iron. For an efficient reduction in thermal load efficiency, the cooling bore is machined inside the upper part of the liner.

The structural safety of all the elements has been confirmed by Finite Element Analysis as well as a thorough testing of the prototype. The piston consists of a steel crown and steel skirt to improve the durability at a high combustion pressure. In addition, an optimized piston bowl shape contributes to reducing the fuel oil consumption. The upper piston ring has a special coating to minimize friction with the cylinder liner, while a newly designed oil scraper ring helps to reduce fuel oil and lubrication oil consumption.

The front end block is made of grey cast iron and it includes a number of cooling water and lubrication oil paths. The auxiliary machinery such as engine driven pumps is also mounted at the front end block for easy access.

Design of the oil seal system of the valve stems

HHI has developed a special valve stem seal system to minimize lubrication oil consumption and prevent contamination of the valves by leaked oil. This offers a much better solution than the conventional O-ring solution. In the as-new situation, the initial oil leak level is similar for the O- ring and the valve stem seal; however, when time increases, the difference of oil leakage between the conventional O-ring and the valve stem seal increases substantially because of wear on the O-ring.

The dual-timing valve technology

The Dual Valve Timing (DVT) technology is applied to improve engine performance, especially in low load conditions. The DVT system is placed inside the cylinder head between rocker arm and push rod. The DVT system can control the amount of intake air to secure sufficient air volume by controlling the intake valve closing time. It contributes to the improvement of engine performance by reducing smoke generation and improves the engine’s acceleration.

Oil leak test result for valve stem seal

Through performance optimization for low load conditions with DVT and swirl creation in the intake port, the HiMSEN H21C has achieved improvement in smoke generation compared with the conventional HiMSEN engine throughout the whole range of engine operation.

The HiMSEN H21C engine is optimized to comply with IMO Tier II; moreover, it is also possible to meet IMO Tier III regulation with the Hyundai NoNOxTM Selective Catalytic Reduction (SCR) system. Furthermore, the exhaust gas scrubbing can be available to reduce SOx emission when high sulphur content fuel is used.

Smoke emission of the HiMSEN H21C

Performance verification

The reliablity of the design has been verified by measurement of a prototype engine through high and low cylcle fatigue endurance tests. The stress, temperature and deformation levels of most components have been measured and the results have been confirmed through a comparison of the analysis results. The combustion performance of the H21C engine has also been confirmed for the entire load conditions by the real-time monitoring and analysis system. The end result is a reliable machine with a very low specific fuel consumption of only 180 g/kWh compared with 184 g/kWh of its predecessor.

Development of the HiLS system

There is a growing demand in the power generation market for Dual Fuel (DF) engines capable of running on natural gas as well as a range of diesel fuels. HiMSEN dual-fuel engines are equipped with a special micro-pilot injector that is always in operation when the engine is running. This injector serves as the igniter when the engine is fuelled by natural gas. In case the engine is running on diesel fuel only, this pilot injector is still in operation in order to avoid clogging of its nozzle. The pilot is responsible for 1% of the fuel supply at full load conditions.

The achieved lower fuel consumption

Optimum engine operation with different fuels has to be ensured, even under different loads. In addition to fuel flexibility, there is a constant desire to improve fuel efficiency and to reduce emissions. As a consequence, modern engines require increasingly advanced systems to control the total engine process, including complex engine sub-systems.

Development of such a sophisticated control system is a time-consuming process that involves many iterative cycles and detailed information exchanges between engineers of different disciplines. This might cause confusion and miscommunication.

Carrying out the development of the control system and checking it with a running engine on a test bench is prohibitively expensive. That is why HHI has developed a Hardware in the Loop Simulation (HiLS) System.

An accurate model of an engine, with all its processes such as intake air manifold flow dynamics, fuel-air mixing, combustion and turbocharger operation, is required if using the real engine is not practical for developing the optimum control strategy. Such a model should not only contain the real processes of the engine at full load conditions, but also give the engine performance during starting, idle running, load changes, fuel changes and stopping. Next to that, the model should represent the engine’s behaviour in real time, since control algorithms and the related hardware also work in real time.

HHI has successfully converted detailed existing engine models that were running in the order of 100 to 1000 times slower than real time into a real-time model. The behaviour of the new model has been thoroughly tested and validated with the actual stationary and dynamic response of an eight-cylinder HiMSEN H35/40DF engine. The end results were very encouraging, since close agreement between the model and the real engine was found. Therefore, trust was created that the new model could be used for testing and optimizing the control strategy and testing of hardware control elements on the engine.

The simulation model gives close to the same values as the real engine test

Illustration of the Engine control system development process

Finally, real-time hardware for HiLS testing was constructed in such a way that it could cover over 250 in/out signals from the generator and yard interfaces, as well as those between engine and controller. Consequently, the simulator could be interconnected with control hardware installed on the real engine.

The HiLS system allows a full optimization of the control strategy as well as checking of the performance of the hardware control sub systems.

Sophisticated technologies developed by HHI enable fast and low-cost optimization for engine design and control systems. The models developed closely predict the actual robustness and performance of the engines.

The models help to develop engines that require less maintenance, which is even made easier. Further, the control systems can be easily tuned to allow low fuel consumption, minimum emissions and an excellent load response.

Ki Hoon Jang is Engineer, HiMSEN Engineering Department 1, Engine & Machinery Division at Hyundai Heavy Industries

Seunghyup Ryu is Senior Researcher, Engine & Machinery Research Institute at Hyundai Heavy Industries

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