the massive-yet-tiny engine a comparison of oem.pdf

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  • Land Warfare Conference 2012 Melbourne Oct/Nov 2012

    The Massive-yet-Tiny Engine: A comparison of OEM claims

    LTCOL BRETT LABOO Senior Military Officer, DSTO

    ABSTRACT Firepower, mobility and protection have not been the sole considerations for modern military platforms for some time now. Auxiliary power generation for an ever increasing range of integrated systems required for the effective and adaptive conduct of network enabled warfare in a connected yet expansive battle space is an additional prime consideration. So too are the through life costs together with the logistic burden for its operation.

    In order to effectively address these considerations holistically and systematically a new or greatly improved technology is required.

    The scope of this work is to compare some COTS/MOTS power packs with a selected new break-through technology for internal-combustion piston enginesthe Massive-yet-Tiny (MyT) engine [1] using only Original Equipment Manufacture (OEM) product specification data. The engines are compared on several criteria, dry weight (kg), gross volume (m), claimed max power output, both (kW) and torque (Nm), specific power (kW/kg) and gross power density (MW/m). Procurement costs and fuel consumption (l/hr) are not considered as they are not universally listed in the OEM product specification literature or websites. Additionally the technology of the MyT engine is described along with an outline of some research and development issues. Finally a number of applications for the MyT engine are discussed briefly.

    The MyT engine clearly outperforms and outclasses all of the COTS/MOTS power packs considered. The 14 MyT engine weighing 68 kg, occupying 0.035 m and with a claimed output of 2238 kW has a minimum specific power of 32.91 kW/kg and a power density of 63.156 MW/m.[2]

    The levels of internal-combustion piston engine efficiency, specific power and power density for the current Australian Defence Force (ADF) inventory are clearly sub-par in comparison to the MyT engine. Notwithstanding any other benefits, there is no valid or logical justification for the Australian Defence Organisation (ADO) to ignore the MyT engine any longer. As a matter of priority the MyT engine needs to be investigated to ratify the claims and verify its reliability so that its output characteristics and general dimensions may be the default essential specifications for power packs across multiple platforms in either block upgrades or initial acquisitions. The Australian Defence Industry has a brilliant opportunity to pre-empt the ADF in the uptake of this technological black swan [3] to the mutual benefit of all parties.

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  • Land Warfare Conference 2012 Melbourne Oct/Nov 2012

    1. Introduction

    Firepower, mobility and protection have not been the sole considerations for modern military platforms for some time now. Auxiliary power generation for an ever increasing range of integrated systems required for the effective and adaptive conduct of network enabled warfare in a connected yet expansive battle space is an additional prime consideration. So too are the through life costs together with the logistic burden for its operation. A whole range of considerations are depicted graphically in a diagram referred to as Quinns Quilt [4], at annex A.

    In order to effectively address the power related considerations holistically and systematically a new or greatly improved technology is required.

    1.1 Scope of Work

    The scope of this work is to compare some COTS/MOTS power packs with a selected new break-through technology for internal-combustion piston enginesMyT engine using only open source / publically available OEM product specification data. The engines are compared on several criteria, dry weight (kg), gross volume (m), claimed max power output, both (kW) and torque (Nm), specific power (kW/kg) and gross power density (MW/m). Gross power density is reported in MW/m so as not to potentially confuse a common metric of kW/l which uses engine capacity. Engine capacity is not considered as it is of limited utility for a comparative analysis of turbine and piston engines. Procurement costs and fuel consumption (l/hr) are not considered as they are not universally listed in the OEM product specification literature or websites.

    Additionally the technology of the MyT engine is described along with an outline of some research and development issues.

    Finally a number of applications for the MyT engine are discussed briefly. It is expected that a reader knowledgeable in the field would identify many additional applicationsand that is encouraged.

    1.2 General History

    The MyT engine has been known in the public domain for almost a decade now. In 2005 it was entered in the NASA Create The Future Contest in the Automotive Category. Not only did it win that category, it was judged as the best entry from all categories that year. [5]. It was publicly displayed at the both the 2005 SEMA Show [6] and the 2006 Los Angeles Auto Show. [7]

    The prototype of the 14 MyT engine weighs only 68 kg, occupies 0.035 m and has a claimed output of 2238 kW. [8] This means that it has a specific power of 32.91 kW/kg and a power density of 63.156 MW/m. Other form-factors include a 6 diameter version. [9]

    2. Description

    Unlike other internal combustion piston engines, the MyT engine pistons do not reciprocate. Moreover they move around the toroidal bore in a staccato motion, mechanically controlled by a gear and crank assembly. There are eight double-headed pistons separately linked into two sets of four permanently fixed and equally spaced interleaved rotors. [10, 11]

    2.1 Pistons and Gears

    A general approximation of the MyT piston could be conceptualised as the joining of two regular pistons back to back which have been cut through in the vicinity of the oil ring. Thus there are no piston skirts and therefore friction losses are minimised. So too are the inertial losses because of the continuous unidirectional motion. The two

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  • Land Warfare Conference 2012 Melbourne October 2012

    interleaved rotors are driven by a very remarkable and inventive sun and planetary gear arrangement. In the basic configuration, one set of gears drives one set of eight pistons i.e. the two rotors. However, the next logical step in the development of the MyT engine is to have the gears drive two sets of eight pistons, i.e. two toroidal bores, one at each end of the crank shaft, astride the centrally mounted gears. [12, 13]

    2.2 Internal Motion

    As the planetary gears rotate around the sun gear the offset linkage point traces out a cycloid. The planetary gears are permanently linked to be exactly out of phase with each other. Thus when one rotor is moving the other is stationary and visa versa. This is the origin of the staccato motion. The MyT engine uses ports for both intake and exhaust and as in normal internal combustion piston engines the ports are opened and closed as the pistons transit past them. In the default configuration the MyT engine is naturally aspirated, yet a logical and rational development path would include various forms of forced induction. The lack of a valve train reduces the parasitic losses incurred by other four stroke internal combustion engines. There are two sets of each type of port and for every two rotations of the crank there are 32 power strokes. In a V8 engine there are just eight in the same 720. [14, 15] The relative motion of the two rotors and gear mechanism is depicted in a spread sheet animation of a stylised model published by the OEM. [16]

    2.3 Other Characteristics

    There are several other novel features of the MyT engine that are of note. Given the external diameter of the toroidal bore is about 13, that makes the stroke length roughly 8 which is remarkably long albeit in an arc. Due to the utilisation of the

    sun and planetary gearing the dwell time at the equivalent of top dead centre is in the order of 12 of crank rotation. This exceptionally long period not only permits but virtually assures almost complete combustion and maximises the transfer of heat into kinetic energy. Hence the only cooling required is that resulting from the incoming charge and conventional fins on the exterior of the engine. Furthermore, the compression ration is variableit ranges from 25:1 up to about 60:1, thus permitting the use of an unusually diverse range of fuels. And, regardless of fuel type consumed it is expected that it would be very efficient. [17, 18, 19]

    2.4 Driven versus Driving

    Not only can the MyT engine operate as an internal combustion engine, but due to its inherent design it can operate very well as a driven device. Although these modalities have not yet been fully explored, initial investigations indicate that the MyT engine shows as much promise in them as it does when operating as an internal combustion engine. The driven modes are somewhat similar. First, when used as a compressor or pump it will deliver both high fluid volumes at high pressure from the one stage. Secondly, it can operate as an air driven motor delivering high torque at low rpm from minimal inputs. [20, 21, 22]

    2.5 Development Issues

    Taken at face value, the claims of the MyT engine seem extraordinary. Thus as part of any rational development programme they and other issues must be successfully addressed in order fully realise and capitalise on this technological advance. Such high power outputs [23] necessarily imply that there would be extreme internal stresses, and pressures. Logically this leads to questions about high strength materials, reliability and maintainability (RAM) and fuel consumption etc.

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  • Land Warfare Conference 2012 Melbourne

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