The present disclosure relates to transport refrigeration units (TRUs) and, in particular, to a TRU with a variable-speed electric refrigeration drive and a variable-speed diesel engine synchronous generator power source.
TRUs for trucks and trailer are evolving toward being configured for full electrical operations. To this end, higher efficiency systems will ultimately need to be developed to enable such full electrical operations. In the meantime, interim solutions that do not involve, for example, battery only electrification, need to be developed that exceed the capabilities of current systems designed to run synchronously. Synchronous systems are characterized in that high engine speed results in high capacity, high airflow and high fuel consumption.
According to an aspect of the disclosure, a transport refrigeration (TRU) system is provided and includes an air management system, a compressor, a generator which generates alternating current (AC) from operations of an engine to power operations of the air management system and the compressor and an AC inverter operably interposed between the generator and the compressor to decouple a drive frequency of the compressor from a frequency of the generator.
In accordance with additional or alternative embodiments, the compressor includes a variable speed compressor.
In accordance with additional or alternative embodiments, the air management system includes parallel air management systems.
In accordance with additional or alternative embodiments, the engine is run at a lowest possible engine speed for needed power and compressor speed is varied based on capacity demand.
In accordance with additional or alternative embodiments, the engine continues to run at the lowest possible engine speed as the capacity demand increases to match a torque demanded from the compressor.
In accordance with additional or alternative embodiments, engine speed increases as the engine approaches a maximum available power.
According to an aspect of the disclosure, a method of operating a transport refrigeration unit (TRU) system including an air management system, a compressor, a generator which generates alternating current (AC) from operations of an engine to power operations of the air management system and the compressor and an AC inverter operably interposed between the generator and the compressor is provided. The method includes decoupling a drive frequency of the compressor from a frequency of the generator.
In accordance with additional or alternative embodiments, the decoupling of the drive frequency of the compressor from the frequency of the generator includes operating the compressor at a variable speed to meet a demand, operating an engine at a lowest possible speed to provide power for the compressor, maintaining operations of the engine at the lowest possible speed as the demand increases and increasing an engine speed of the engine as available power of the engine approaches a maximum.
According to an aspect of the disclosure, method of operating a transport refrigeration unit (TRU) system in which a drive frequency of a compressor is decoupled from a frequency of a generator is provided. The method includes operating the compressor at a variable speed to meet a demand, operating an engine at a lowest possible speed to provide power for the compressor, maintaining operations of the engine at the lowest possible speed as the demand increases and increasing an engine speed of the engine as available power of the engine approaches a maximum.
In accordance with additional or alternative embodiments, the operating of the engine includes determining whether the engine is operating within a desired load range.
In accordance with additional or alternative embodiments, the operating of the engine further includes maintaining an engine speed if the engine is operating within the desired load range.
In accordance with additional or alternative embodiments, the operating of the engine further includes increasing an engine speed if the engine is not operating within the desired load range and more engine power is required.
In accordance with additional or alternative embodiments, the operating of the engine further includes reducing engine power and decreasing engine speed if the engine is not operating within the desired load range and more engine power is not required.
In accordance with additional or alternative embodiments, the operating of the compressor includes determining whether a TRU temperature error is greater than zero.
In accordance with additional or alternative embodiments, the operating of the compressor further includes decreasing a compressor drive frequency if the TRU temperature error is not greater than zero and not equal to zero.
In accordance with additional or alternative embodiments, the operating of the compressor further includes decreasing a compressor drive frequency if the TRU temperature error is greater than zero and an engine load is greater than a maximum load range.
In accordance with additional or alternative embodiments, the operating of the compressor further includes maintaining the compressor drive frequency if the TRU temperature error is not greater than zero and is equal to zero.
In accordance with additional or alternative embodiments, the operating of the compressor further includes maintaining the compressor drive frequency if the TRU temperature error is greater than zero and if the engine load is not greater than a maximum load range, more engine power has been requested and engine power has not been increased.
In accordance with additional or alternative embodiments, the operating of the compressor further includes maintaining the compressor drive frequency if the TRU temperature error is greater than zero and if the engine load is not greater than a maximum load range, more engine power has been requested, engine power has been increased and the compressor is at a maximum drive frequency.
In accordance with additional or alternative embodiments, the operating of the compressor further includes increasing a compressor drive frequency if the TRU temperature error is greater than zero and if the engine load is not greater than a maximum load range, more engine power has been requested, engine power has been increased and the compressor is not at a maximum drive frequency.
Additional features and advantages are realized through the techniques of the present disclosure. Other embodiments and aspects of the disclosure are described in detail herein and are considered a part of the claimed technical concept. For a better understanding of the disclosure with the advantages and the features, refer to the description and to the drawings.
For a more complete understanding of this disclosure, reference is now made to the following brief description, taken in connection with the accompanying drawings and detailed description, wherein like reference numerals represent like parts:
As will be described below, a refrigeration compressor drive frequency is decoupled from a primary diesel generator frequency using a refrigeration compressor variable speed AC inverter that is located between a 3-phase diesel synchronous generator and the compressor. The approach will be to allow the engine to run at lowest possible engine speeds for needed power while allowing the refrigeration system to vary operations of the primary compressor and if needed fan speeds based on capacity demands. As refrigeration power demand increases, the engine can stay in a lowest speed required to match torque demanded from the compressor and fan systems with intent of staying in lowest speed required to match demand of the refrigeration or compressor system. If engine power is approaching a maximum available power, the engine will increase in rpm to thereby increase available engine power to thus supply the AC inverter with power needed for the refrigeration compressor.
With reference to
The TRU can include an engine and is configured to generate a cooling (or heating) airflow that can be directed into the interior 122 so as to control at least a temperature of the interior 122. In this way, in an exemplary case in which the items being transported are perishable and need to be refrigerated (or heated), the TRU 130 can maintain the interior 122 in a refrigerated (or heated) state even during hot (or cold) days.
As shown in
With continued reference to
The TRU system 301 further includes a generator 310, an alternating current (AC) inverter 320 and a variable speed compressor 330. The TRU system 301 further includes an air management system 340 (see
The TRU system 301 of
With continued reference to
If the engine 302 is within the desired load range for the TRU control, engine rpm is maintained 504. Conversely, if the engine 302 is not within the desired load range for the TRU control, it is determined whether more engine power is required from the TRU control 505 (see a determination of whether more engine power is requested at block 513 to be discussed below). If more engine power is not required, engine power is reduced 506 and engine rpm is decreased 507 and control reverts to considering whether the engine 302 is within a desired load range for TRU control 502. If more engine power is required, engine rpm is increased 508 and control reverts to considering whether the engine 302 is within a desired load range for TRU control 502.
If the TRU temperature error is not greater than zero, it is determined whether TRU temperature error equals zero 509. If the TRU temperature error does not equal zero, a compressor drive frequency of the compressor 131 is decreased 510 and control reverts to determining whether the TRU temperature error is greater than zero 503. If the TRU temperature error equals zero, the compressor drive frequency is maintained 511 and control reverts to determining whether the TRU temperature error is greater than zero 503.
If the TRU temperature error is greater than zero, it is determined whether engine load is greater than a maximum load range 512. If the engine load is greater than the maximum load range, the compressor drive frequency is decreased 510 and control reverts to determining whether the TRU temperature error is greater than zero 503. If the engine load is not greater than the maximum load range, more engine power is requested 513 and it is determined whether engine power has been increased to a desirable load range 514. If the engine power has not been increased to the desirable load range, the compressor drive frequency is maintained 511 and control reverts to determining whether the TRU temperature error is greater than zero 503. If the engine power has been increased to the desirable load range, it is determined whether the compressor 131 is at a maximum drive frequency 515. If the compressor 131 is at the maximum drive frequency, the compressor drive frequency is maintained 511 and control reverts to determining whether the TRU temperature error is greater than zero 503. If the compressor 131 is not at the maximum drive frequency, the compressor drive frequency is increased 516 and control reverts to determining whether the TRU temperature error is greater than zero 503.
With reference to
Technical effects and benefits of the present disclosure are the provision of systems in which compressor operations are decoupled from primary diesel engine speed to thereby allow for maximized fuel efficiency gains arising from compressor capacity maximizations as needed with lowest possible engine speeds. The systems allow for maximum total efficiency BTUs/lb_fuel as well as 75% of TRU run time in low-power conditions, which will allow for low fuel burn rates and reduced noise. The systems also allow for engines to run at peak torque for maximized refrigeration load as needed as well as smaller and less costly TRU engines with wide speed ranges of about 600-2500 rpm for example. Use of the systems can provide for cases in which high engine speeds would only be needed for short durations characterized by high power demand associated with high ambient conditions.
The corresponding structures, materials, acts, and equivalents of all means or step-plus function elements in the claims below are intended to include any structure, material, or act for performing the function in combination with other claimed elements as specifically claimed. The description of the present disclosure has been presented for purposes of illustration and description, but is not intended to be exhaustive or limited to the technical concepts in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the disclosure. The embodiments were chosen and described in order to best explain the principles of the disclosure and the practical application, and to enable others of ordinary skill in the art to understand the disclosure for various embodiments with various modifications as are suited to the particular use contemplated.
While the preferred embodiments to the disclosure have been described, it will be understood that those skilled in the art, both now and in the future, may make various improvements and enhancements which fall within the scope of the claims which follow. These claims should be construed to maintain the proper protection for the disclosure first described.
This application claims the benefit of Provisional Application No. 63/115,909 filed Nov. 19, 2020, the disclosure of which is incorporated herein by reference in its entirety.
Number | Date | Country | |
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63115909 | Nov 2020 | US |